Deconstructing Dinosaur Doomsday with Chicxulub Simulations

A gravity anomaly map of the Chicxulub Crater area superimposed on the Yucatan Peninsula shows areas of mass concentrations (i.e., the yellow and red areas are ‘gravity highs’ whereas the green and blue areas are ‘gravity lows’), according to NASA. The aftermath of the impact led to the extinction of about 75% of all species on Earth, the space agency adds. Photo :NASA

The meteorite hit in the Yucatan sometime about 66 million years ago, and the Earth was immediately remade. More than 300 gigatons of sulfur and 400 gigatons of carbon dioxide were ejected 25 kilometers high into the atmosphere in mere seconds, enveloping the Earth in gases that blocked the sun for years. The shock wave wiped out life, and triggered tsunamis, landslides and hurricane-force winds generally across the globe.

“Proposed kill mechanisms for the K-Pg mass extinctions include the following: short-term cooling and darkness produced by dust, soot, and sulfur in the atmosphere ; long-term warming from the release of massive volumes of carbon dioxide; ocean acidification; and global firestorms ignited when ejecta heats up as it reenters the Earth's atmosphere and emits thermal radiation,” they write.

The team from the Planetary Science Institute and Imperial College London used advanced 3-D computer modeling to determine the effects of the meteor. The software used is called the multiphase hydrocode SOVA, which is a 3-D modeling program that includes difference dimensions of strong shock wave physics involving materials of different size, shape, weight, and layers, they explain. (The code is not open for public use, the authors note).

Based on the crater, and the current best estimates, they place the projectile that struck Chicxulub at 12.2 kilometers diameter with a mass of 2,500 gigatons – traveling at a staggering 18 kilometers per second. It collided with the surface of our planet at a 60-degree angle, they estimate.

The tremendous energy right at the point of impact sent a ripple of death across the planet, they write.

“When an impact-induced shock wave of sufficiently high pressure passes through sedimentary rocks, they decompose and form part of the expanding impact plume,” they write. “For Chicxulub, where seawater, porous carbonates, and evaporates formed the upper portion of the target, this process led to the injection of carbon dioxide, sulfur-bearing gases, and water vapor into the atmosphere.”

After the fire swept clean the Earth, surface temperatures were reduced by 20 degrees Celsius for about 30 years, according to the models. Oceans remained markedly cooler for centuries, they add.

“In these circumstances,” they continue, “sulfur rapidly forms an aerosol, which backscatters and absorbs solar radiation causing rapid cooling at the Earth’s surface, while the addition of carbon dioxide contributes to longer-term warming.”

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